f. Changes to landing gear, such as internal parts of shock struts, length, geometry, or brakes and brake
systems,
is listed under the category of:
404. ALTERATIONS REQUIRING ACO ENGINEERING APPROVAL
Items (a) through (o) in the following list of typical alterations will most likely require engineering
approval, and often require an STC. Items in (p) do not normally require an STC but will usually require
ACO engineering assistance.
The fact that you highlighted this in order to bolster your claim demonstrates that perhaps you read what you wanted to see, not what it actually says. This is not meant to offend, we all do it. But, this is clearly stated in your own copy of the text.
David, as I said, this discussion is not meant to change your mind. Do what you want to, however no matter how strong your opinion on the matter. The statement you've made:
is in fact groundless unless you have some data to back it up. Nor does it change the manufacturer's specifications or the FAA definition of a major alteration.. I know it's good enough for you, but that doesn't make it the best practice. Engineers don't determine these standards based on personal opinion; they use the laws of physics, established methodology, and extensive testing.I would argue the tailwheel main spring and 'eye bolt' are sufficiently similar in type, shape, materials and dimensions to the L-19 to have NO appreciable affect on weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness. The only difference is a slight increase in thickness that has no affect on performance.
Bruce, are you implying that because the part is PMA'd, it is therefore safe to install on the aircraft of our choice? If so, why can't we just plant any piece of equipment on our aircraft if it has a PMA? Why bother with so many STC's? You are probably right about the metallurgy of springs allowing for equivalent strengths at different thickness. Typically the goal is to provide greater strength in a smaller spring, though, for dimensional limitations of the installation. What sense would it make to put a larger, heavier spring of the same strength on an aircraft? The name of the game is weight savings, so by what logic could one assume that a PMA'd replacement would be designed to be heavier with no strength gain, nor (as you said), any appreciable increase in life span?